From 52c1820cb4b5f10c0664104bb6f570305d0c49cc Mon Sep 17 00:00:00 2001 From: Christian Melki Date: Mon, 30 Apr 2012 11:21:26 +0200 Subject: [PATCH 042/117] 8250.c: less than 2400 baud fix. commit f9a9111b540fd67db5dab332f4b83d86c90e27b1 upstream. We noticed that we were loosing data at speed less than 2400 baud. It turned out our (TI16750 compatible) uart with 64 byte outgoing fifo was truncated to 16 byte (bit 5 sets fifo len) when modifying the fcr reg. The input code still fills the buffer with 64 bytes if I remember correctly and thus data is lost. Our fix was to remove whiping of the fcr content and just add the TRIGGER_1 which we want for latency. I can't see why this would not work on less than 2400 always, for all uarts ... Otherwise one would have to make sure the filling of the fifo re-checks the current state of available fifo size (urrk). Signed-off-by: Christian Melki Signed-off-by: Greg Kroah-Hartman [bwh: Backported to 3.2: adjust filename; replace *port with up->port] Signed-off-by: Ben Hutchings --- drivers/tty/serial/8250.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/tty/serial/8250.c b/drivers/tty/serial/8250.c index eeadf1b..70585b6 100644 --- a/drivers/tty/serial/8250.c +++ b/drivers/tty/serial/8250.c @@ -2327,10 +2327,11 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, quot++; if (up->capabilities & UART_CAP_FIFO && up->port.fifosize > 1) { - if (baud < 2400) - fcr = UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_1; - else - fcr = uart_config[up->port.type].fcr; + fcr = uart_config[up->port.type].fcr; + if (baud < 2400) { + fcr &= ~UART_FCR_TRIGGER_MASK; + fcr |= UART_FCR_TRIGGER_1; + } } /* -- 1.7.9.5